N-azolyl sulfenamides

ABSTRACT

WHEREIN R IS ALKYL, CYCLOALKYL, ARALKYL, ARYL OR SUBSTITUTED ARYL, WHERE THE SUBSTITUENTS ARE ALKYL, ALKOXY, NITRO, CHIORO, BROMO, FLUORO, IODO OR HYDROXY R&#39;&#39; IS HYDROGEN, LOWER ALKYL, CYCLOALKYL, OR R&#34;S-WHERE R&#34; HAS THE SAME MEANING AS R AND MAY BE THE SAME OR DIFFERENT FROM R, T IS AZOLYL OR SUBSTITUTED AZOLYL SELECTED FROM THE GROUP OF THIAZOLYL, BENZOTHIAZOLYL, BENZOXAZOLYL, AND SUBSTITUTED DERIVATIVES THEREOF, WHERE THE SUBSTITUENTS ARE LOWER ALKYL, CHLORO, BROMO, FLUORO, IODO, NITRO OR LOWER ALKOXY ARE PREMATURE VULCANIZATION INHIBITORS OF VULCANIZABLE ELASTOMERS.   T-N(-R&#39;&#39;)-S-R   SULFENAMIDE OF THE FORMULA

United States Patent O F 3,770,758 N-AZOLYL SULFENAlVIIDES Joseph EdwardKerwood, Akron, Ohio, assignor to Monsanto Company, St. Louis, M0.

N Drawing. Continuation-impart of application Ser. No. 861,152, Sept.25, 1969, now Patent No. 3,645,987, dated Feb. 29, 1972. Thisapplication Oct. 14, 1971, Ser. No. 189,133

Int. Cl. C07d 91/46 US. Cl. 260305 11 Claims ABSTRACT OF THE DISCLOSURESulfenamide of the formula TNS-R wherein R is alkyl, cycloalkyl,aralkyl, aryl or substituted aryl, where the substituents are alkyl,alkoxy, nitro, chloro, bromo, fluoro, iodo or hydroxy, R is hydrogen,lower alkyl, cycloalkyl, or R"S where R" has the same meaning as R andmay be the same or different from R, T is azolyl or substituted azolylselected from the group of thiazolyl, benzothiazolyl, benzoxazolyl, andsubstituted derivatives thereof, where the substituents are lower alkyl,chloro, bromo, fluoro, iodo, nitro or lower alkoxy are prematurevulcanization inhibitors of vulcanizable elastomers.

REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 861,152, filed Sept. 25,1969, now US. Pat. 3,645,987, issued Feb. 29, 1972.

BACKGROUND OF THE INVENTION The invention relates to new compoundsuseful as inhibitors of premature vulcanization in rubber.

In the manufacture of vulcanized rubber products, crude rubber iscombined with various other ingredients such as fillers, accelerators,and antidegradants to alter and improve processing of the rubber and toimprove the properties of the final product. The crude rubber is putthrough several steps in the plant before it is ready for the final stepof vulcanization. Generally the rubber is mixed with carbon black andother ingredients except the vulcanizing agent and accelerator. Then thevulcanizing and accelerating agents are added to this masterbatch in aBanbury mixer or a mill. Scorching, viz, premature vulcanization, canoccur at this stage of the processing, during the storage period beforevulcanizing, and during the actual vulcanization. After the vulcanizingand accelerating agents are added, the mixture of crude rubber is readyfor calendering or extruding and vulcanization. If prematurevulcanization occurs during the storage of the crude mixture or duringprocessing prior to vulcanization, the processing operations cannot becarried out because the scorched rubber is rough and lumpy, consequentlyuseless. Premature vulcanization is a major problem in the rubberindustry and must be prevented in order to allow the rubber mix to bepreformed and shaped before it is cured or vulcanized.

SUMMARY OF THE INVENTION I have discovered a class of sulfenamides whichare extremely valuable inhibitors of premature vulcanization. They arecharacterized by an azolyl group on the sulfenamide nitrogen and may berepresented by the formula T-III-S-R where R is alkyl, cycloalkyl,aralkyl, aryl, or alkaryl. R is hydrogen, lower alkyl, cycloalkyl or RSwhere R has the same meaning as R but is not necessarily the same "iceradical as R, T is thiazolyl, benzothiazolyl, or benzoxazolyl. Aryl is aunivalent organic radical the free valence of which belongs to anaromatic carbocyclic nucleus and not to a side chain. Both unsubstitutedand substituted aryl and alkaryl radicals are suitable for practice ofthe present invention. The substituents may be alkyl as indicated above(alkaryl) or alkoxy, nitro, chloro, bromo, fiuoro, iodo or hydroxy. -Itis preferred that the carbocyclic nucleus represented by R contain notmore than one electronegative substituent. Aryl radicals of 6 to 12nuclear carbon atoms are preferred. Alkyl radicals are aliphaticradicals of the series C H The alkyl radical may be primary, secondaryor tertiary and the primary alkyl may be branched or unbranched. Alkylradicals of 1-18 carbon atoms are preferred and a preferred subgroup arealkyl radicals of 3-12 carbon atoms. Lower alkyl means alkyl of 1-5carbon atoms. The preferred cycloalkyl radicals contain 5-12 carbonatoms in the ring a preferred subgroup thereof containing 58 carbonatoms.

The azole radicals may be substituted or unsubstituted suitablesubstituents being lower alkyl, chloro, bromo, rfluoro, iodo, nitro orlower alkoxy.

More specific examples of R are methyl, ethyl, propyl, isopropyl, butyl,isobutyl, sec. butyl, t-butyl, amyl, sec. amyl, tert-amyl, n-hexyl,2-ethylhexyl, decyl, dodecyl, phenyl, naphthyl, benzyl, a, ot'-dimethylbenzyl, phenethyl, 3-phenyl propyl, 4-phenylbutyl, p-chlorophenyl,p-nitrophenyl, xenyl, o-tolyl, m-tolyl, p-tolyl, xylyl, p-nonylphenyl,p-t-butylphenyl, cyclopentyl, cyclohexyl, cyclooctyl 01' cyclododecyl.Other examples of suitable azole radicals are 4-methylthiazolyl,S-methylthiazolyl, 4-ethylthiazolyl, 4-chlorobenzothiazolyl,5-chlorobenzothiazolyl, 6-ethoxybenzothiazolyl,5,6-dimethylbenzothiazolyl, 6-methoxybenzothiazolyl andd-nitrobenzothiazolyl. Ingeneral the carbocyclic ring of benzothiazolyl,or benzoxazolyl may be substituted by lower alkyl, lower alkoxy, halogenor nitro.

Examples of the new compounds of the invention are: N- 2-b enzothiazolylethylsulfenamide, N-(Z-benzothiazolyl)-t-butyl-sulfenamide,

N- 2-benzothiazolyl-n-hexylsulfenamide,

N- (Z-benzothiazolyl cyclohexylsulfen amide,

N-(2-benzothiazolyl)phenylsulfenamide,

N-(2-benzothiazolyl)-p-chlorophenylsulfenamide,

N-(Z-benzothiazolyl)-p-nitrophenylsulfenamide,

N-(2-benzothiazolyl)-N-ethylthio ethylsulfenamide,

N- (Z-benzothiazolyl) -N-cyclohexylthio cyclohexylsulfenamide,

N-(Z-benzothiazolyl)-N-(methy1)-propylsulfenamide,

N- Z-benzoxazolyl -N- (n-butyl) -phenylsulfenamide,

N- (2-benzothiazolyl) -N- (cyclohexyl) phenylsulfenamide,

N(2-benzothiazolyl)-N-(methyl)-p-chlorophenylsulfenamide,

N- Z-b enzothiazolyl -N- (tert-butyl cyclopentylsulfenamide,

N- 2-benzothiazolyl -cyclooctylsulfenamide,

N- (2-benzothiazolyl)-N-phenylthio phenylsulfenamide,

N-(Z-benzoxazolyl)ethylsulfenamide,

N- 2-benzoxazolyl -t-butylsulfenamide,

N-(2-benzoxazolyl)-n-hexylsulfenamide,

N- (2-b enzoxazolyl cyclohexylsulfenamide,

N-(Z-benzoxazolyl)phenylsulfenamide,

N- 2-benzothiazolyl) -N- (methyl) ethylsulfenamide,

N-(2-benzothiazolyl)-N-(ethyl)-t-butylsulfenamide,

N- (Z-benzothiazolyl -N- (methyl -n-hexylsulfenarnide,

N- (Z-benzothiazolyl) -N- (propyl) -cyclohexylsulfenamide,

N- Z-benzothiazolyl) -N- propyl) phenylsulfenamide,

N-(Z-thiazolyl)ethylsulfenamide,

N- Z-thiazolyl -t-butylsulfenamide,

N-(Z-thiazolyl)-n-hexylsulfenamide,

N-(Z-thiazolyl)-cyclohexylsulfenamide,

3 N- (Z-thiazolyl) phenylsulfenamide, N- [2- (4-chlorobenzothiazolyl)ethylsulfenamide, N- [2- 4chlorobenzothiazolyl) ]-t-butylsulfen amide,N- [2 4-chlorob enzothiazolyl) ]-n-hexylsulfen amide, N- 2-(4-chlorobenzothiazolyl) cyclohexylsulfenamide, N- [2- (4-chl0robenzothiazolyl) ]phenylsulfen amide, N- [2- (5 -chlorobenzothi azolyl)ethylsulfenamide, N- 2- 5 -chlorob enzothiazolyl) ]-t-butylsulfenamide,N- [2- 5 -chlorobenzothi azolyl ]-n-hexylsulfenamide, N- [2- 5 -chlorobenzothiazolyl) cyclohexylsulfenamide, N- [2- S-chlorobenzothiazolyl)phenylsulfen amide, N- [2- (6-ethoxybenzothiazolyl) 1 -ethylsulfenamide,N- [2- 6-ethoxyb enzothiazolyl) ]t-butylsulfenamide, N- [2-6-ethoxybenzothiazolyl) ]-n-hexylsulfenamide, N- [2-6-ethoxybenzothiazolyl) ]cyclohexylsulfenamide, N- [2-6-ethoxybenzothiazolyl) phenylsulfenamide, N- [2- (5,6-dimethylbenzothiazolyl) ]ethylsulfen amide, N- [2- (5,G-dimethylbenzothi azolyl) ]-t-butylsulfenamide, N- [2- (5, G-dimethylbenzothiazolyl) ]-n-hexylsulfenamide, N- [2- 5,6-dimethylbenzothiazolyl)cyclohexylsulfen amide, N- 2- (5 ,G-dimethylbenzothiazolyl)phenylsulfenarnide, N- [2- (5 ,6-dimethylb enzothiazolyl) ]-N- (methyl)ethylsulfenamide, N- [2- (5 ,6-dimethylbenzothiazolyl) ]-N- (propyl) -nhexylsulfenamide, N- [2- (5 ,6-dimethylbenzothiazolyl) ]-N- (ethyl)-cyclohexylsulfenamide, and N- [2- (5,6-dimethylbenzothiazolyl) ]-N-(methyl) phenylsulfenamide.

Rubber stocks containing delayed-action accelerators can be used in theprocess of this invention. Cheaper, more scorchy accelerators can alsobe used withan excellent degree of improvement. The improved vulcanizingprocess of this invention can be used advantageously to process stockscontaining other types of blacks and fillers used in rubber compounding.The invention is also applicable to gum stocks.

The invention is applicable to rubber mixes containingsulfur-vulcanizing agents, peroxide-vulcanizing agents, organicaccelerators for vulcanization, and antidegradants. The new compoundsdirectly increase process safety of peroxide cures and are preferablyused in the absence of organic accelerator when peroxide is thevulcanizing agent. With sulfur-vulcanizing agents organic acceleratorwill normally be present. Sulfur-vulcanizing agent means elementalsulfur or sulfur containing vulcanizing agent, for example, an aminedisulfide or a polymeric polysulfide. Peroxide-vulcanizing agent meansany of the organic peroxides which are curing agents for natural andsynthetic rubber. One well-known curing agent is dicumyl peroxide. Thetechnical literature describes in detail various procedures to effectperoxide cures. Certain patents also described the use ofperoxide-vulcanizing agents, typical of which are US. 2,819,255 and2,819,256 (1958).

The invention is applicable to vulcanization accelerators of variousclasses. For example, rubber mixes containing the aromatic thiazoleaccelerators which include N-cyclohexyl-Z-benzothiazolesulfenamide,N,N-dialkyl-2-benzothiazolesulfenamide, Z-mercaptobenzothiazole,N-tert-butyl-Z-benzothiazolesulfenamide, Z-benzothiazolyldiethyldithiocarbamate, 2,Z'-dithiobisbenzothiazole and2-(morpholinothio)benzothiazole may be used. Amine salts ofmercaptobenzothiazole accelerators, for example, the t-butylamine salt,morpho line salt or 2,6-dimethyl morpholine salt ofmercaptobenzothiazole may be used in the invention. Any of the thiazoleaccelerators may be used. Stocks containing accelerators, for example,tetramethylthiuram disulfide, tetramethylthiuram monosulfide, aldehydeamine condensation products, thiocarbamylsulfenamides, thioureas,xanthates, and: guanidine derivatives, aresubstantially improved usingthe process of my invention. Examples of thiocarbamylsulfenamideaccelerators are shown in US. Pats. 2,381,392, Smith assigned toFirestone; 2,388,236, Cooper assigned to Monsanto; 2,424,921, Smithassigned to Firestone; and British Pt. 880,912, Dadson assigned toImperial Chemical Industries Limited. The invention is applicable toaccelerator mixtures. The invention is applicable to stocks containingamine antidegradants. Rubber mixes containing antidegradants, forexample, N-1,3- dimethylbutyl-N-phenyl-p-phenylenediamine, N,N' bis-(1,4-dimethylpentyl) p phenylenediamine, and other phenylenediamines,ketone, ether, and hydroxy antidegradants and mixtures thereof, aresubstantially improved using the process of my invention. Mixtures ofantidegradants, for example, a mixture ofN-1,3-dimethylbutyl-N-phenyl-p-phenylenediamine and N,N'-bis(l,4-dimethylpentyl)-p-phenylenediamine, furnish a much improved finalproduct When used with the inhibitors of this invention.

The inhibitors of my invention can be used in natural and syntheticrubbers and mixtures thereof. Synthetic rubbers that can be improved bythe process of this invention include cis-4-polybutadiene, butyl rubber,ethylone-propylene terpolymers, polymers of 1,3-butadiene, for example,1,3-butadiene itself and of isoprene, copolymers of 1,3-butadiene withother monomers, for example, styrene, acrylonitrile, isobutylene, andmethyl methacrylate. The invention relates to diene rubbers, and theterms rubbers and diene rubbers are synonymous for the purpose of thisinvention.

The amount of inhibitor used depends upon the other components in therubber formulation, the vulcanizing agent used, the accelerator used,the antidegradant used and other process variables which may be uniqueto a specific application. An experienced compounder can readilydetermine the amount needed for any particular situation. The amountusually is within the range of 0.1 to 5 parts by Weight per parts byweight of elastomer, and more often within the range of 0.3 to 2 partsby weight. The preferred usage generally falls within the range of 0.5and 1.5 parts by weight inhibitor.

The compounds may be prepared by reacting the corresponding sulfenylchloride with 2 aminothiazole, 2- aminobenzothiazole, 2aminobenzoxazole, N alkyl-2- aminobenzothiazole, or a substitutedderivative thereof in the presence of a hydrogen chloride acceptor. Thegeneral reaction is where n is 1 or 2 and R and T have the same meaningas before. If diiferent R substituents are desired Where n is 2, onemole of RSCl is reacted initially followed by reacting a difierent RSClwith H RSN-T formed in the initial reaction.

An alternate method for preparing the compounds comprises reactingthiomide with an N-substituted-Z-aminoazole. Examples of suitablethioimides are shown in US. 3,546,185, Dec. 8, 1970. The reaction isillustrated by the equation it it typical examples follow:

EXAMPLE 1 N-(Z-benzothiazolyl)phenylsulfenamideN-(2-benzothiazolyl)phenylsulfenamide is prepared in the followingmanner: 14.4 grams (0.1 mole) of benzene sulfenyl chloride dissolved in38.6 grams of CCl is added dropwise over a 20-30 minute period between20-30 C. to a stirred slurry containing 15.0 grams (0.1 mole) of2-aminobenzothiazole, 10.0 grams (0.128 mole) of pyridine, and 200 m1.of benzene. The slurry is held with stirring for One hour, filtered, andwashed with benzene. The soluble portion is recovered by evaporation ofthe benzene and is a pink solid. The material is recrystallized fromethyl acetate to yield 6.0 grams of a solid which melts at 160 C. withdecomposition. Analysis of the product gives 10.72% nitrogen and 24.98%sulfur. Calculated percentages for C H N S are 10.77% nitrogen and 24.8%sulfur.

EXAMPLE 2 N- (2-benzothiazolyl isobutylsulfenamideN-(2-benzothiazolyl)isobutylsulfenamide is prepared by the addition of97 m1. of a n-pentane solution containing 0.2 mole of isobutyl sulfenylchloride dropwise over a 15 minute period to a stirred solution of 15.0grams (0.1 mole) of Z-aminobenzothiazole and 25.0 grams of triethylaminedissolved in 150 m1. of N,N-dimethyl formamide (DMF) cooled to C. Thetemperature is maintained between 0-7 C. by cooling with an external icebath. The cooling bath is removed and the reaction mixture is stirredfor 2 hours. The reaction mixture is filtered to remove triethylaminehydrogen chloride. An oil is separated from the filtrate by addition of3.0 liters of ice water. The oil is extracted with one pound of ether bydecanting the water away from the ether layer. The ether solution isdried over 100 grams of anhydrous sodium sulfate. The material isrecovered by evaporation of the ether solution. The yellowish orangesolid so recovered is recrystallized twice from heptane. The productmelts at 9799 C. Analysis of the product gives 11.72% nitrogen and27.03% sulfur compared to 11.78% nitrogen and 26.9% sulfur calculatedfor C H N S EXAMPLE 3 N- 2-benzothiazolyl) -n-hexylsulfenamide N (2benzothiazolyl)-n-hexylsulfenamide is prepared in the same manner asN-(2-benzothiazolyl)isobutylsulfenamide in Example 2 except n-hexylsulfenyl chloride is used in place of isobutyl sulfenyl chloride. Theproduct is recrystallized from heptane melts at 70-72" C. Analysis ofthe product shows 10.14% nitrogen and 23.15% sulfur. Calculatedpercentages for C H N S are 10.53% nitrogen and 23.05% sulfur.

EXAMPLE 4 N- (2-benzothiazolyl) cyclohexylsulfenamideN-(2-benzothiazolyl)cyclohexylsulfenamide is prepared in the followingmanner: 140 ml. of a solution containing 37.5 grams (0.25 mole) ofcyclohexyl sulfenyl chloride in n-pentane is added slowly over a 30minute period of a stirred solution of 37.5 grams (0.25 mole) of 2-aminobenzothiazole and 30.0 grams (0.3 mole) of triethylamine dissolved in250 ml. of DMF. The temperature rises from 25 C. to 30 C. The reactionis quenched by the addition of 2.5 liters of ice water to the slurry.The amine salt is dissolved and a thick viscous oil results. Afterdecanting the water from the oil layer, other is added to the oil layerfrom which a tan solid is crystallized overnight. The tan solid isslurried in a 50/50 mixture of heptane and ethyl alcohol and isfiltered. 38.0 grams of a white solid is obtained. This material isrecrystallized from toluene two times to yield 27.0 grams of a solid,which melts at 156-158 C. Analysis of the product indicates 10.37%nitrogen and 24.13% sulfur compared to 10.62% nitrogen and 24.20% sulfurcalculated for C H N S EXAMPLE 5 N(2-benzothiazolyl)-N-(phenylthio)phenylsulfenamide 28.8 grams (0.2 mole)of benzene sulfenyl chloride dissolved in 86.2 grams of CCL; is addedover a 30 minute period to a stirred solution of 15.0 grams (0.1 mole)of 2-aminobenzothiazole and 25.0 grams (0.2 mole) of triethylamine in150 m1. of DMF cooled to 5 C. The temperature is maintained between -5and 10 C. during which a yellow orange precipitate forms. The reactionmixture is allowed to warm to room temperature. The reaction is quenchedby the addition of ice water and a gummy semisolid forms. Afterdecanting the water, a reddish solid is obtained by filtration. Thismaterial is recrystallized twice from heptane to give a solid whichmelts with decomposition at 112-115 C. A portion of the sample isreduced with NaI and is titrated with sodium thiosulfate to give anassay which confirms a bis-substituted compound. Analysis of the productshows 7.68% nitrogen compared to 7.28% nitrogen calculated for rs m z a-EXAMPLE 6 N- (5,6-dimethyl-2-benzothiazolyl) cyclohexylsulfenamideCyclohexyl sulfenyl chloride (0.25 mole) dissolved in 150 ml. ofn-pentane is added dropwise over a 30 minute period to a stirredsolution of 44.5 grams (0.25 mole) of 5,6-dimethyl-Z-aminobenzothiazoleand 30.0 grams of triethylamine in 200 ml. of DMF at room temperature. Aslight rise in temperature is observed. The mixture is stirred two hoursthen quenched with two liters of water. After decanting the water, theoil layer is extracted with benzene and dried over sodium sulfate. Uponevaporation of the benzene, 69.0 grams yield) of product is obtained.Recrystallized from toluene, the product is a white solid which melts at153-155 C.

EXAMPLE 7 N-(Z-thiazolyl) -N-(cyclohexylthio)cyclohexylsulfenamideCyclohexyl sulfenyl chloride dissolved in 300 ml. of npentane is addedto Z-aminothiazole and triethylamine in 200 ml. of DMF at roomtemperature. The reaction mixture is quenched with water and the organiclayer extracted with ether. Evaporation of the ether gi-ves 78.7 gramsof product.

EXAMPLE 8 N- (Z-benzothiazolyl) -2,4-dinitrophenylsulfenamide2,4-dinitrobenzene sulfenyl chloride (0.05 mole) in ml. of CCl., isadded dropwise over a period of 30 minutes to a solution of2-aminobenzothiazole (0.05 mole) and pyridine (0.064 mole) in 750 ml. ofDMF at room temperature. The mixture is stirred for one hour and theCCL, removed by evaporation. One liter of water is added and theprecipitate is recovered by filtration. The solid is washed withisopropanol, filtered and dried. The product melts at 225-227 C.

EXAMPLE 9 N-methyl-N- (2-b enzothiazolyl) phenylsulfenamide Phenylsulfenyl chloride (0.02 mole) in 12 ml. of benzene and triethylamine(0.03 mole) are added to N-meth yl-2-aminobenzothiazole (0.02 mole) atroom temperature. After stirring overnight, the mixture is filtered toremove the triethylamine salt. The filtrate is evaporated to give thedesired product which after recrystallization from isopropanol melts at112-113 C. Identification is confirmed by nuclear magnetic spectroscopy.Analysis of the product gives 61.92% carbon, 4.57% hydrogen, 10.38%nitrogen and 23.49% sulfur compared to 61.7% carbon, 4.4% hydrogen,10.2% nitrogen and 23.5% sulfur calculated for C H N S EXAMPLE 10N-methyl-N-(2-benzothiazolyl)cyclohexylsulfenamide A mixture ofN-methyl-Z-aminobenzothiazole (0.23 mole) andN-(cyclohexylthio)phthalimide (0.23 mole) in 300 ml. of ethanol isheated at reflux with stirring for four hours. The mixture is cooled andstirred at room temperature for 24 hours. 700 ml. of water containing0.3 mole of NaOH are added to convert the phthalimide by-product to thesoluble salt. The mixture is cooled to C. and filtered to recover theproduct which is washed with water and air dried. The white solidproduct isrecovered in 97% yield, M.P. crystallized from heptane 6364 C.Analysis gives 10.06% nitrogen and 23.21% sulfur compared to 10.06%nitrogen and 23.03% sulfur calculated for C H N S EXAMPLE 1 lN-cyclohexyl-N- (2-benzothiazolyl) cyclohexylsulfenamide A mixture ofN-cyclohexyl-2-aminobenzothiazole (0.2 mole) andN-(cyclohexylthio)phthalirnide (0.2 mole) in 300 ml. of ethanol isheated at reflux for four hours and stirred at 25-30 C. for 18 hours.600 ml. of water containing 0.25 mole of NaOH is added. After stirring15 minutes, one liter of ether is added. The ether layer is separated,washed with water until neutral and dried over sodium sulfate. The etheris removed in vacuum at the maximum temperature of 80-90 C. at 1-2 mm.Hg to give a viscous liquid which is identified as the desired product.Analysis gives 8.25% nitrogen and 18.37% sulfur compared to 9.08%nitrogen and 18.51% sulfur calculated for CIQHZGNZSZ.

EXAMPLE 12 N-propyl-N-(2-benzothiazolyl)- cyclohexylsulfenamide Amixture of N-propyl-2-aminobenzothiazole (0.2 mole) andN-(cyclohexylthio)phthalimide (0.2 mole) in 300 ml. of ethanol areheated at reflux for five hours. 500 ml. of water containing 0.25 moleof NaOH is added and the mixture is filtered to remove some unreactedstarting material. The filtrate is extracted with ether and the productremoved by evaporation. Analysis gives 8.85% nitrogen and 21.18% sulfurcompared to 9.14% nitrogen and 20.93% sulfur calculated for C H N SEXAMPLE 13 N-ethyl-N-(2-benzothiazolyl)- cyclohexylsulfenamideN-(Z-thiazolyl)cyclohexylsulfenamide To a reactor, there is charged2-aminothiazole (0.1 mole), N-(cyclohexylthio)phthalimide (0.1 mole) and200 ml. of heptane. The mixture is heated at reflux for six hours andfiltered hot to separate phthalimide. The filtrate is evaporated to givea red precipitate which is recrystallized from hexane to give thedesired product, M.P. 8284 C. Identification is confirmed by NMR.

EXAMPLE 15 N-propyl-N-(2-benzoxazolyl) cyclohexylsulfenamide A mixtureof N-propyl-Z-benzoxazolyl (0.1 mole) ar d N-(cyclohexylthio)phthalimidein 200 ml. of heptane is heated for six hours at reflux. The mixture isfiltered hot to remove phthalimide. The filtrate is evaporated and theresidue taken up in hexane. Additional phthalimide and reactants arerecovered from the hexane fraction.

Evaporation of the hexane gives an oil which is identified as thedesired product.

The following tables illustrate the improved processing safety obtainedby incorporating the new compounds into rubber. For all the rubberstocks tested and described, infra, as illustrative of the invention,Mooney scorch times at 121 C. are determined by means of a Mooneyplastometer. The time in minutes (t required for the Mooney reading torise five points above the minimum viscosity is recorded. Longer timesare indicative of the activity of the inhibitor. Longer times on theMooney Scorch Test are desirable because this indicates greaterprocessing safety. Percentage increases in scorch delay are calculatedby dividing the Mooney scorch time of the stock containing the prematurevulcanization inhibitor by the Mooney scorch time of the control stock,multiplying by 100, and subtracting 100. These increases show thepercentage improvement in scorch delay over the control stock whichcontains no inhibitor. Additionally, cure ratings are calculated fromthe time required to cure the natural rubber stocks at 144 C. andsynthetic rubber stocks at 153 C. Curing characteristics are determinedby means of the Monsanto Oscillating Disc Rheometer described by Decker,Wise, and Guerry in Rubber World, December 1962, p. 68. From therheometer data the maximum torque is recorded in rheometer units, t isthe time in minutes for a rise of two rheometer units, above the minimumreading and 1 is the time required to obtain a torque 90% of themaximum.

The trademarks of some compounds used in the practice of this inventionare Santocure MOR, Santocure NS and Santoflex l3. MOR is the accelerator2-(morpholinothio)benzothiazole and NS is the accelerator N-tert-butyl-2 benzothiazolesulfenamide. Santoflex 13 is the anti degradantN-(1,3-dimethyl butyl)-N-phenyl-p-phenylenediamine.

The compounds of this invention are excellent premature vulcanizationinhibitors. In a natural rubber masterbatch, the scorch delay isincreased 186% when N-(2- benzothiazolyl)phenylsulfenamide is used.

Masterbatch: Parts Smoked sheets Furnace black (*ISAF) 45 Zinc oxide 3Stearrc acid 2 Hydrocarbon softener 5 Total parts 155 Stock A B C D E FG Masterbatch 155.0 155. 0 155.0 155.0 155. 0 155. 0 155. O

Sulfur 2. 5 2. 5 2. 5 2. 5 2. 5 2. 5 2. 5

Santocure MOR 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5

N-(Z-benzothiazolyl) phenylsnlfenamide 1. 0 N-(2-benzothiazolyl)-N-(phenylthio) phenylsulfenamide- 1. 0 N-(Z-benzothiazolyl)isobutylsulfenamide 1. 0 N-(2-benzothiazolyD-nhexyl nlfpnamida 1, 0N-(2-benzotbiazolyl) cyclohexylsulfenam- N -(5,6'dimethylbenzothiazolyl)cyclohexylsulfenamide 1. 0 Santoflex l3 2. 0 2. 0 2. 0 2. 0 2. 0 2. 0 2.0 Mooney scorth at 25. 7 73. 1 67. 5 52. 3 47. 8 65. 5 86. 7 Percentincrease in scorch delay 186 162 104 86 155 l 146 Rheometer at 144 0.:

Maximum torque.-- 59. 0 64. 7 62. 9 64. 4 62. 2 59. 9 67. 0 8.0 16.2 17.0 14. 5 13. 3 14. 6 20. 3 no 22. 5 33. 3 31. 6 29. 0 27. 3 30. 7 41. 0

1 This stock was run at a difierent time and the control it was 35.2minutes.

In an oil-extended styrene-butadiene rubber masterbatch, scorch delay isincreased 122% when one part ofN-(Z-benzothiazolyl)cyclohexylsulfenamide is used and 9 50% when 0.4part of N-methyl-N-(2-benzothiazolyl) cyclohexylsulfenamide is used.

Masterbatch': Parts SBR 1712 137.5 Furnace black (ISAF) 65 .0 Zinc oxide3.0 Stearic acid 1.0 Hydrocarbon softener i 1.5

Total parts 20 8.0

Stock H I J K Masterbateh" 208. 208. 0 208. 0 208. 0

Sulfur 1. 7 1. 75 2. 0 2. 0

Santocure N 1.2 1. 2 1. 0 1. 0

N-(Z-benzothiazolyl)cyclohexylsulfenamide. 1. 0

N-methyl-N-(2-benzothiazolyl) cyclohexyl nlfen amide 4 Santofiex 13 2. 02. 0 2. 0 2. 0

Mooney scorch at 121 0.:

17. 5 38. 8 22. 0 33. 0 Percent increase in scorch delay 122 50Rheometer at 153 0.:

Maximum torque 53. 5 51. 8 49. 0 49. 0 7. 9 13. 0 9. 5 11. 3 21.2 27. 25 26. 5

The premature vulcanization inhibitor activity of other compounds of theinvention is illustrated in a natural rubber masterbatch.

Santofiex 13 Mgoney scorch at 121 Percent increase in scorch delay Thecompounds of this invention where R is aryl or alkyl have bactericidalproperties. Such compounds are toxic to a spectrum of microorganisms,including S. aureus, S. typhosa, PS. aeruginosa, and A. niger.

Although the invention has been illustrated by typical examples, it isnot limited thereto. Changes and modifications of the examples of theinvention herein chosen for purposes of disclosure can be made which donot constitute departure from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A compound of the formula wherein R is alkyl of 1-18 carbon atoms,cycloalkyl of 5-8 carbon atoms, aral'kyl of 7-10 carbon atoms or aryl of6-12 nuclear carbon atoms, or substituted said aryl, Where thesubstituents are alkyl of 1-9 carbon atoms, methoxy, ethoxy, nitro,chloro, bromo, fiuoro, iodo or hydroxy, R' is hydrogen, lower alkyl,cycloalkyl of 5-8 carbon atoms or R"S Where R" has the same meaning as Rand may be the same or difierent from R, T is benzothiazolyl, andsubstituted derivatives thereof, Where the substituents are lower alkyl,chloro, bromo, iiuoro, iodo, nitro, methoxy or ethoxy.

2. A compound according to claim 1 wherein R is alkyl, cycloalkyl, oraryl, R is hydrogen or alkylthio, cycloalkylthio, arylthio, and T isbenzothiazolyl.

3. A compound according to claim 1 wherein R is alkyl, cycloalkyl, oraryl, R is hydrogen and T is benzothiazolyl.

4. The compound according to claim 3 wherein R is n-hexyl.

5. The compound according to claim 3 wherein R is isobutyl.

6. The compound according to claim 3 wherein R is cyclohexyl.

7. The compound according to claim 2 wherein R is phenyl, R isphenylthio, and T is benzothiazolyl.

8. A compound according to claim 1 wherein R is aryl or cycloalkyl, R isH or R"S where R" is aryl or cycloalkyl and T is benzothiazolyl.

9. A compound according to claim 1 wherein R is alkyl, cycloalkyl, oraryl, R is lower alkyl and T is benzothiazolyl.

10. The compound according to claim 9 wherein R is cyclohexyl and R' ismethyl.

11. The compound according to claim 9 wherein R is phenyl and R ismethyl.

References Cited UNITED STATES PATENTS 3,645,987 2/1972 Kerwood 260305RICHARD J. GALLAGHER, Primary Examiner US. Cl. X.R.

26'079.5 B, 306.8 R, 307 D, 309.2, 9.9.9

